The present invention relates to an ice making machine, and more particularly, to a type installed on a boat and capable of making large amount of ice from sea water.
Known is a drum type ice making machine which includes an upstanding drum covered with an adiabatic member. The drum has an inner wall provided with a cooling medium chamber through which cooling medium is recirculated. A hollow rotary shaft is rotatably disposed at a central portion of the drum, and water is sprinkled toward an inner peripheral surface of the drum through the rotary shaft. The sprinkled water is frozen at the drum inner surface during its downward travel therealong. Thus frozen ice is scraped by a blade fixedly secured to the rotary shaft, and is discharged from the lower portion of the drum.
According to the conventional ice making machine of this type, since the cooling medium passes from the upper to the lower portion of the cooling medium chamber, heat exchanging efficiency relative to the sprinkled water at the upper portion of the inner wall would be higher than that at the lower portion thereof, so that uniform freezing would not be attainable over the entire inner wall of the drum.
Further, according to the conventional device, a plurality of nozzles are radially formed along the length of the hollow rotary shaft, and water is ejected through these nozzles toward the drum wall, so that uniform water adhesion to the wall may not be obtainable, to thereby provide irregularity in freezing. As a result, freezing efficiency may be degraded. Furthermore, water not converted into ice may be disadvantageously dripped into the scraped ice and is mixed therewith.
In order to overcome the above-mentioned drawbacks, an improved ice machine is provided as described in Japanese Utility Model early publication No. 57-2376 (1982). In the publication are provided a plurality of cooling medium chambers arranged in vertical direction and between an outer adiabatic member and an inner wall, and cooling inlet and outlet are connected to each of the chambers. A hollow rotary shaft is rotatably disposed at the central portion of the drum. The upper portion of the shaft is connected to an output shaft of a driving motor through a power transmission mechanism, while the lower portion of the shaft is provided with a water passage connected, through a rotary joint, to a water supply pipe connected to a water tank. An ice scraping blade is fixedly secured to the rotary shaft at the side of the shaft and ranging the total axial lengths of the cooling medium chamber. A water sprinkling pipe radially outwardly extends from the upper portion of the rotary shaft, and has one end connected to the water passage. The other end of the water sprinkling pipe is positioned adjacent the upper portion of the inner drum surface, and is formed with a water sprinkling hole. At the lower portion of the drum is provided a gradually inclined surface whose lower end is connected to an annular recess for receiving water.
The improved ice making machine would be available for freezing ordinary sea water when the device is installed on a vessel or boat. However, such machine would not be sufficiently available for freezing sea water containing therein high salinity and/or impurities such as plankton and minerals. Further, even if the water is frozen at the drum wall, the frozen ice may be slippingly rotated relative to the drum wall by the rotational urging force of the blade, that is, the ice is rotated together with the rotation of the blade. Therefore, sufficient ice scraping operation and ice withdrawal may not be attainable.